Portable electronic chord organ



Sept i, y K. D. RUPPERT 352677@ PORTABLE ELECTRONIC CHORD ORGAN INVENTOR L3 KEITH D. RUPPERT l, H970 KL D. RUPPERT PORTABLE ELECTRONIC GHOR@OHGAN Sept 4 Sheets-Sheet 2 Filed Jan. D', 1966 Sept. 1, 1970 K. D.RUPPERT 3,526,700

PORTABLE ELECTRONIC CHORD ORGAN Filed Jan. 5, 1966 f 4 Sheets-Sheet 3 8OUT INVENTOR KEITH D. RUPPERT SGP- w70 k. D. RUPPERT PORTABLE ELECTRONICOHORO ORGAN` 4 Sheets-Sheet 4.

O Filed Jan. s, 196s 30mV MAX s STRING 2'5 K 'mAPAsON A FIGB FIGIZ KE|THD. RUPPERT ATTORN United States Patent Office 3,526,799 Patented Sept.l, 1970 3,526,700 PORTABLE ELECTRONIC CHORD ORGAN Keith D. Ruppert,Decatur, Ill., assignor to General Electric Company, a corporation ofNew York Filed Jan. 3, 1966, Ser. No. 518,086 Int. Cl. @h 1/06, 5/04,5/12 US. Cl. SLL-1.01 7 Claims ABSTRACT 0F THE DISCLOSURE This inventionrelates to electronic musical instruments, and more particularly toelectronic chord organs which are portable and have large numbers ofnotes and instrument sounds.

Heretofore, low priced organs have been limited to the small, electricblower powered, vibrating reed type. These are limited to only one voiceand they need an AC. outlet to function. The present invention is an allelectronic organ which can be constructed economically by printedcircuit techniques and therefore can satisfy a public desired for a lowcost wide range electronic organ. Also, the organ of the presentinvention may be battery operated, adapting the organ due to thisfeature and its small size, to be used as a portable musical instrumentfor outdoor entertaining.

The present invention also provides for a plurality of different soundsby the use of electronic iiltering circuits which operate onharmonically rich input waves to shape the input waves in accordancewith patterns normally produced by known musical instruments. Also, theportable electronic organ of the present invention is adapted to produceboth the chords and the melody, by only single fingered playing.

The invention is carried out by a preferred| embodiment which comprisesa number of transistorized Hartley oscillators and a plurality ofsynchronized relaxation oscillators for producing a large number ofavailable notes, each output wave f orm of the Hartley oscillators andrelaxation oscillators being rich in harmonics, a plurality of voicefilters for shaping the input waves to have desired sounds and beingselectively connected to the output amplifier, buses which carry theoscillator outputs to the iilters, and switching means responsive to thekeys on the organ keyboard for selecting a musical chord combination ofnotes to be connected to the buses.

It is therefore an object of the present invention to provide a new andimproved electronic organ.

It is a further object of the present invention to provide a new andimproved portable electronic chord organ.

It is another object of the present invention to provide a new andimproved switching means such that both chords and melody may beproduced by single iingered playing.

It is yet another object of the present invention to provide new andimproved tone generator circuitry comprising a master oscillator andrelaxation oscillator dividers which synchronize reliably and haverelatively low current drain.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention, as illustratedin the accompanying drawings wherein,

FIG. 1 is a block diagram of the oscillator arrangement for producingthe available musical notes;

FIG. 2 is a schematic diagram of the Hartley oscillator and frequencydivider of the present invention;

FIG. 2A shows, in simplified form, a typical prior art neon bulb typerelaxation oscillator circuiti;

FIG. 2B shows a sawtooth waveform which may be created by discharge ofthe capacitor in the circuit of FIG. 2A;

FIG. 2C shows an exaggerated waveform at the first divider of thecircuit shown in FIG. 2;

FIG. 3 is a `schematic of a portion of a switching arrangement which maybe used in the present invention;

FIG. 4 is a block diagram of the voicing and output section of thepresent invention;

FIGS. 5 and 6 are schematics of amplifiers useful in the presentinvetnion; and

FIGS. 7-14 are schematics of iilters useful in the present invention.

In FIG. 1 there is shown a general block diagram of the available noteproducing system of the present invention. Each block, 12 through 34,represents a Hartley oscillator plus relaxation oscillator frequencydividers in combination, and the musical notes produced by eachcombination is indicated by the letter inserted in the block. A powersupply for providing operating voltages for the oscillators is indicatedby block 10.

Blocks 12 through 26 have four outputs each, indicating that theycomprise one transistorized Hartley oscillator and three synchronizedneon bulb relaxation oscillators, whereas the three outputs from each ofblocks 28 through 34 indicates that they each comprise a single Hartleyoscillator plus only two synchronized neon bulb relaxation oscillators.The total available notes produced by the above described system in apreferred embodiment of the invention, and their frequencies are givenbelow.

AVAILABLE NOTES AND THEIR F REQUENCIES Note Oscillator- Divider 1Divider 2 Divider 2, 093. 0 1, 046. 5 523. 25 261. 63 l, 975. 5 987. 77493. 88 246. 94 1, 864. 7 932. 33 i 1,760.0 880. 0 1,661.2 830.61 1,568.0 783.99 1,480. 0 739. 99 l, 396. 9 698. 46 l, 318. 5 659. 2b 1, 244. 5622. 2G 1,174. 7 587. 33 l, 108. 7 554. 37

Thus, it can be seen that in a preferred embodiment of the presentinvention 44 notes are available to the organ player.

A preferred circuit for the blocks 12 through 34 is indicated in FIG. 2,wherein there is shown a Hartley transistorized oscillator 60 and threeneon =bulb relaxation oscillators 40, 42and 44. The Hartley oscillator60` comprises a sigle transistor 62 and a tank circuit 36 which is tunedto a desired frequency corresponding to a desired musical note.

The differences between this Hartley oscillator circuit 60 and theconventional shunt-fed Hartley oscillator circuit reside in the mannerof obtaining the output and in the shape of the output waveform. In aconventional circuit, the output is taken across the coil, or a portionthereof, and it is nearly a perfect sine wave. In the present invention,the output is taken from the transistor collector, across anincompletely bypassed load resistor R2 and supply terminal L2. It shouldbe noted that terminal L2 is the +9 volt supply terminal, L1 is the +90volt supply terminal, and L3 is the ground terminal. The capacitor C4across the load resistor R2 makes the circuit a semi-differentiator sothat the output wave form is nearly a sawtooth. The sawtooth wave isrich in harmonies and has a much better shape for synchronizing therelaxation oscillators than does a pure sine wave.

The frequency dividers which produce submultiples of the Hartleyoscillator output frequency are neon bulb relaxation oscillators whchare synchronized by the sawtooth output from the Hartley oscillator.

For an understanding of the mode of operation of the neon bulbrelaxation oscillators 40, 42, and 44, including the manner wherebytheir capacitors C5, C7 and C9 charge through their respective resistorsR4-R5, R9R10, and R14-R15, attention is now directed to FIGS. 2a, 2b,and 2c. FIG. 2a shows, in its simplest form, a typical prior art neonbulb type relaxation oscillator. The capacitor C charges toward thesupply voltage V at a rate determined by the RC time constant. The neonbulb Ne is not conducting during this period so it is a high impedanceacross the capacitor C and has practically no effect on the capacitor Ccharging. The capacitor C continues to charge until the neon bulbbreakdown voltage is reached. At this point, the bulb Ne ionizes and itsirnpedance drops to a low value. Current then ows through the neon bulbNe and the capacitor C discharges through the bulb Ne at a ratedetermined by the RC time constant of the capacitor C and the lowequivalent impedance of the bulb Ne. The discharge of the capacitor Ccontinues until the extinquishing voltage of the neon bulb Ne isreached. At that time, the bulb Ne quits conducting and reverts back toits high impedance state and the capacitor C starts charging again. Theequivalent impedance of the conducting bulb Ne is much less than R, sothe capacitor C discharges much faster than it charges, creating asawtooth waveform as shown in FIG. 2b. The neon bulb relaxationoscillator of FIG. 2a will free run at a frequency determined by the sumof the charge and discharge time. This free running frequency is equalto one over that sum.

T o use the neon bulb relaxation oscillator of FIG. 2a as a frequencydivider, the free running frequency is made to be slightly below thedesired frequency and pulses from a synchronizing oscillator are addedinto the circuit in such a manner that every second pulse adds to thepeak of the sawtooth waveform, thereby causing the neon bulb to ionizeand start conducting immediately. The range over which such asynchronizing voltage is effective is determined by the relativemagnitudes of the sawtooth waveform and of the synchronizing pulse.

In accordance with the present invention, the synchronizing voltage forthe tone generator circuit of FIG. 2 is obtained from junction ofresistors R3 and R6. These resistors form a voltage divider across themaster oscillator output, since the full output voltage can not be used.An important aspect of this invention is the reliable synchronization,which is achieved primarily by returning all of the neon bulbs 46, 48and S0 to ground through the same voltage divider resistor R6. Thisinsures that the synchronizing pulse will be added to the voltagealready across the bulb due to the charge on the capacitor.

Another important aspect of this invention is that this circuit (FIG. 2)synchronizes on the negative-going portion 0f the synchronizing pulserather than on the positive-going portion, as is the conventionalmethod. As an example, consider the operation of the iirst divider 40AThe synchronizing voltage substracts from the voltage across the neonbulb 46 twice during one cycle of the rst divided 40. When the secondsynchronizing pulse starts decreasing, the voltage across the bulb 46,which is already near the breakdown voltage of the bulb 46, willincrease at a rapid rate, causing the `bulb 46 to ionize, thussychronizing it at half the master oscillator frequency. The waaeform atthe iirst divider 40 is shown in FIG 2c. The sychronizing pulses areexaggerated in FIG. 2c to emphasize their action. The dotted line inFIG. 2c shows the shape of the free running waveform.

Another important aspect of this invention is the fact that the dividersoperate with an extremely low current drain. This makes it possible forthe life of the 90 v. battery to be nearly equal to shelf life.

In viewing the circuit of FIG. 2 it should be noted that the voicingresistors VR1, VR2, VRS, and VR.,x are isolating resistors which servetwo functions. These voicing resistors not only isolate the oscillators40, 42, and 44 from each other, but they also help to set the desiredoscillator output levels.

Particular values of the circuit parameters which may be used inconstructing oscillators to provide the 44 notes listed above areindicated below.

VOICING RESISTO RS NOTE-Filter input, 1.3.13 volts.

OSCILLATOR AND DIVIDER CAPACITORS C1 C2 C3 C4 C5 Ca C1 OSCILLTOR ANDDIVIDER RESISTORS R1 Rz Rx R4 Rs Re R1 Re R10 R12 R14 R15 R11 3. 9K 47068K 1M 3M 120K 560K 1M 3M 560K 1M 3l 560K 3. 9K 470 68K 1M :iD/I 120K560K 1M 3M 560K 1M 31W 560K 3. 9K 470 68K 1M 3M 120K 560K 1M 3M 560K INI3M 560K 5. 6K 470 68K 1M SNI 120K 560K Il Sii/I 560K INI SVI 560K 5. 6K470 68K 1M 3M 120K 560K IM 3M 560K 11W 31u 5601( 5. 6K 470 68K 1M 3M102K 560K Il 3M 560K Il 3M 560K 6. 8K 470 68K Il 3M 120K 560K 1M BNI560K INI 3l\/I 560K 6. 8K 470 68K 1li/I 3M 120K 560K: Il Bhf 5601( 11W3M: 560K 6. 8K 470 68K Il 3M 120K 560K 11 BM 560K 6. 8K 470 68K 1M 3M120K 560K 1M 31W 6. 8K 470 68K 1M 3M 120K 560K 1M 31W 6. 8K 470 68K 1M3M 120K 560K Il BNI Selected ones of the available notes are thenapplied to the buses which include an eight-foot bus, a third bus, afifth bus, and a four-foot bus, as indicated in FIG. 3. As will beunderstood by those skilled in the musical arts, the eight-foot buscarries the fundamental frequency and the four-foot bus carries theoctave frequency, and third and fifth refer to the third and fifth notesof the major scale which, in conjunction with the fundamental, form themajor triad. For the 44 available notes listed above, the organ keyboardcontains 32 keys which are depressed by the played to produce the melodyand chords desired. Each key connects four different available notes tothe four buses respectively, as noted.

In FIG. 3, only a portion of the switching circuitry is shown toillustrate how the desired combinations of notes may be connected to thebuses. For example, when key number 8 on the keyboard is depressed,contacts 70 are closed connecting note C4 (indicating the C noteproduced by frequency divider 3-see the list of available notes above)to the eight-foot bus, the E3 note to the third bus, the G3 note to thefifth bus, and the C3 note to the four-foot bus. As a second example,when key number 7 of the keyboard is depressed,.notes B4, D#3, F#3, andB3 are connected respectively to the eight-foot bus, third bus, fifthbus, and four-foot bus. The remaining 30 keys connect other notes to thebuses in accordance with the following table:

KEY SWITCHES Keys 8 bus 3rd bus 5th bus 4 bus 1.F F4 A4 o4 F3 F114 A114G13 F113 a. G4 134 D3 G3 4. G1114. o4 D113 G113 5A A4 C113 E3 Aa 6A A114D3 F3 A113 7.13 B4 D113 F113 Bs 8.o o4 n3 G3 o3 9.o C113 F3 G13 C112 D3F113 A3 D2 D113 G3 A113 D112 E3 G11?, n3 F2 F3 A3 o3 F2 F113 A13 C112F112 G3 B3 D2 G2 G11?, o3 D112 G1112 As C12 F2 A2 A13 D2 F2 A112 B3 D12F112 B2 C3 F2 G2 o2 G12 F2 G12 C111 D2 F112 A2 D1 D112 G2 A112 D11 E2G12 B2 E1 F2 A2 o2 F1 F112 A112 C11 F111 G2 B2 D1 G1 G112 o2 D111 G11112 C11 F1 A1 A112 D1 F1 A111 D111 F11 B1 F1 G1 o1 The switching circuitsdescribed above allow a player to play the organ in a conventionalmanner, forming chords with the players hands, and also allows one toplay with a single finger and obtain both the melody and the chords.Although in the above described embodiment there is available thefundamental, third, and fifth, etc. forming a major triad, in a largerembodiment of the invention, there would be available more notes so onecould also obtain minor triads, seventh chords, etc.

The remainder of the electronic organ, including the connections betweenthe buses and output speaker 100, is shown in FIG. 4. The notes on theeight-foot bus, the third bus, and the fifth bus, are applied, whenswitches and 112 are closed through a pre-amplifier 148 to theeight-foot filters 132 through 142. The particular eight-foot filter orfilters connected into the circuit is a matter of choice and iscontrolled by switches 118 through 128 which are locate/d near thekeyboard within easy reach of the player. The note on the four-foot busis applied through pre-amplifier 150 to the fourfoot filters 144 and 146which are selectively inserted into the circuit by means of panelswitches 114 and 116, also within easy reach of the player. The filteroutputs are connected to an amplifier 130 which in turn applies itsoutput to the loud speaker 100.

Although the pre-amplifiers 148 and 150 and the amplifier 130 may havevarious designs, particular pre-amplifier and amplifier circuits whichare suitable for use in the present invention are indicated by thecircuit diagrams in FIGS. 5 and 6. In FIG. 5, each pre-amplifiercomprises two stages of grounded emitter amplification and in FIG. 6 theamplifier 130 comprises a first grounded emitter stage which drives anoutput push pull stage which in turn drives the speaker 100.

Referring back to FIG. 4, the filters, 132 through 146, when connectedinto the circuit, receive periodic wave forms which are rich inharmonics, and are designed to shape these wave forms in accordance withshapes normally associated with various musical instruments. Althoughthe voicing system of FIG. 4 includes eight lters, 132 through 146, itis not limited to those filters shown. Since the tones are produced byfiltering harmonically rich electrical waves, any number as well as anytype of voices can be produced. However, in a preferred embodiment ofthe invention, filters 132 through 142 may be designed as shown in FIGS.7 through 12 respectively, and filters 144 and 146 may be designed asshown in FIGS. 13 and 14 respectively.

It should be noted that switches 110, 112, 114 and 116 may all bedisconnected, thereby allowing the depression of a single key on thekeyboard to produce only a single note rather than an entire chord.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. A portable electronic chord organ comprising (a) a number nOftransistor Hartley oscillators for producing n different notes on themusical scale,

(b) n groups of frequency dividers, each group connected to a particularone of said oscillators for producing notes at submultiples of the noteproduced by the particular oscillator, whereby the total number ofseparate notes produced is equal to the sum of all oscillators, andfrequency dividers,

(c) an amplifier having its output connected to a loud speaker,

(d) first and second pre-amplifiers,

(e) an eight-foot bus, a third bus, a fifth bus, and

a four-foot bus,

(f) a keyboard having a plurality of depressable keys,

(g) switching means `responsive to the depression of a key on thekeyboard for connecting four notes to said buses respectively wherebyeach key depression causes a different combination of four notes to beconnected to said buses and each combination represents a musical triadplus octave, the notes of the triad being connected to the eight-footbus, third and fifth buses respectively and the octave note beingconnected to the four-foot bus, said four-foot bus being connected tothe input of said second preamplifier and said eight-foot bus beingconnected to the input of said first pre-amplifier,

(h) first and second bus switches for connecting said third bus and saidfifth bus, respectively, to the input of said first pre-amplifier,

(i) a plurality of filters for imparting different sounds to the notesapplied thereto, a first group of said plurality of filters havinginputs applied thereto from the output of said first pre-amplifier, anda second group of said plurality of filters having inputs appliedthereto from the output of said second pre-amplifier, and

(j) switching means for connecting selected ones of said plurality offilters to the input of said amplifier.

2. The portable electronic chord organ as claimed in claim 1 whereineach frequency divider comprises a neon bulb relaxation oscillatorhaving a free running frequency slightly below the desired submultipleof the Hartley oscillator frequency with which said relaxationoscillator is associated, and voltage divider means connecting theoutput of the associated Hartley oscillator to the relaxation oscillatorfor synchronizing the relaxation oscillator for synchronizing therelaxation oscillator.

3. The portable electronic chord organ as claimed in claim 2 whereineach said Hartley oscillator comprises a tuned L-C circuit and a singletransistor, the output from each of said Hartley oscillators being takenfrom the collector of the transistor.

4. An electronic chord organ comprising (a) twelve transistoroscillators for producing twelv different notes on the musical scale,

(b) twelve groups of frequency dividers, each group connected to aparticular one of said oscillators for producing notes at submultiplesof the note produced by the particular oscillator, whereby the totalnumber of separate notes produced is equal to the sum of all oscillatorsand frequency dividers,

(c) an amplifier having its output connected to a loudspeaker,

(d) a preamplifier means,

(e) an eight-foot bus, at least two intermediate buses including a firstintermediate bus and a second intermediate bus, and a four-foot bus,

(f) a keyboard having a plurality of depressible keys,

(g) switching means responsive to the depression of a key on thekeyboard for connecting at least four notes to said buses, respectively,whereby each key depression causes a different combination of notes tobe connected to said buses and each combination represents a musicaltriad plus octave, the note of the triad being connected to theeight-foot bus and to two of said intermediate buses respectively, andthe octave note being connected to the four-foot bus, said fourfoot busbeing connected to a first input of said preamplifier means and saideight-foot bus being connected to a second input of said pre-amplifiermeans,

(h) intermediate bus switches for connecting said intermediate buses tosaid preamplifier means,

(i) a plurality of filters for imparting different sounds to the notesapplied thereto, said filters having inputs applied thereto from saidpre-amplifier means, and

(j) switching means for connecting selected ones of said plurality offilters to the input of said amplifier.

5. The electronic chord organ as claimed in claim 4 wherein eachfrequency divider comprises a neon bulb relaxation oscillator having afree running frequency slightly below the desired submultiple of anassociated transistor oscillator frequency and voltage divider meansconnecting the output of the associated transistor oscillator to therelaxation oscillator for synchronizing said relaxation oscillator.

6. The electronic chord organ as claimed in claim 5 wherein eachrelaxation oscillator includes a neon bulb, and the voltage dividermeans includes connections of all of said neon bulbs to ground through asingle voltage divider resistor.

7. The electronic chord organ as claimed in claim 4 wherein each groupof frequency dividesr associated with the first eight transistoroscillators comprises three relaxation oscillators, each group offrequency dividers associated with the remaining four transistoroscillators comprising two relaxation oscillators.

References Cited UNITED STATES PATENTS 2,128,367 8/1938 Kock 84-1.25 X3,099,700 7/1963 Bergman 84-1.19 3,379,820 4/1968 Olson 84-1.24

WARREN E. RAY, Primary Examiner U.S. Cl. XR.

SLi-1.04, 1.11, 1.19

